Mixed Material Cathode for Secondary Alkaline Batteries

ABSTRACT

A secondary alkaline battery using manganese dioxide is described. The battery includes a mixed cathode material with birnessite-phase manganese dioxide or electrolytic manganese dioxide (EMD), a bismuth compound and a copper compound selected from the group consisting of elemental copper and a copper salt. In some embodiments, a conductive carbon and/or a binder may also be included.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority to U.S.application Ser. No. 15/394,975 filed Dec. 30, 2016, which is acontinuation of and claims priority to International Application No.PCT/US2015/055215 filed Oct. 13, 2015, which claims priority to U.S.Provisional Application No. 62/062,983 filed Oct. 13, 2014 and U.S.Provisional Application No. 62/067,215 filed Oct. 22, 2014, the entiretyof which are incorporated herein by reference.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under grant numberDEAR0000150 awarded by the U.S. Department of Energy. The government hascertain rights in the invention.

BACKGROUND OF THE INVENTION

This disclosure relates to batteries including electrochemical cells.Alkaline manganese dioxide cells have been predominantly used as primarybatteries. However, the one-time use of primary batteries results inlarge material wastage as well as undesirable environmentalconsequences. Also, potential economic losses can arise due to thesignificant imbalance between the energy that is required to manufacturethese cells compared to the energy that can be actually stored. As aconsequence, there is a clear advantage to convert primary cells torechargeable or secondary cells.

Manganese dioxide has proven recalcitrant to this necessary conversiondue to fundamental problems with its crystal structure and sidereactions which result in products that are not amenable tocharge-discharge cycling. Efforts to develop the zinc-manganese dioxidebattery system date back more than forty years, with many unsuccessfulattempts made to commercialize it. Secondary (rechargeable) alkalinebatteries have recently been marketed using a technology disclosed inU.S. Pat. No. 4,957,827. These rechargeable alkaline batteries requireproprietary chargers that improve cycleability (U.S. Pat. No.7,718,305). However, their lifetime is limited due to fall off incapacity at the high depths of discharge that are of interest in manycommercial applications. Due to these limitations, rechargeable alkalinebatteries have not yet witnessed widespread adoption.

The theoretical capacity that a manganese dioxide crystal can dischargeis 617 mAh/g, which is based on the incorporation of two electrons inthe redox reaction. To access this capacity during the dischargeprocess, the manganese dioxide crystal must undergo stressful phasetransformations and chemical reaction steps that may lead to itseventual breakdown and loss of rechargeable material. To control theselattice dilations and chemical transformations, the cycled capacity hasusually been limited to 5 to 10% of the overall capacity. Wroblowa etal. (EP0138316A1 and U.S. Pat. No. 4,451,543) found that synthesizingthe birnessite-phase of manganese dioxide, and incorporating bismuth andlead in the crystal structure through physical or chemical meansimparted rechargeability characteristics to the manganese dioxidematerial. In some cases, they were able to obtain up to 80-90% of thesecond electron capacity. Yao (U.S. Pat. No. 4,520,005) found a way ofincorporating bismuth and lead in the birnessite-phase of the manganesedioxide in a single step reaction. Yao's method was a variation of theoriginal synthesis method by Wadsley (JACS, Vol 72, 1781, 1950).Rechargeable Battery Corporation (U.S. Pat. No. 5,952,124 and U.S. Pat.No. 5,156,934) developed methods for synthesizing oxides or hydroxidesof bismuth coated on manganese dioxide and heating nitrates of bismuthand manganese to create a phase of bismuth-manganese dioxide. The priorart shows that bismuth plays a role in lattice stabilization and inavoiding the electrochemical inactive phase of hausmannite (Mn₃O₄)during cycling. However, none of the prior art could develop high cyclelife with good reliability and reproducibility. Extensive testingindicates that within a few charge-discharge cycles the depth ofdischarge obtainable falls off rapidly with a large loss of capacity.Also, it was found that the high cycle life obtained in the publicationsrelied on cycling the material potentiodynamically, a cycling protocolthat cannot be used in real world applications, rather thangalvanostatically which is a preferred protocol to cycle batteries inreal world applications. Potentiodynamic cycling is an experimentalmethod in electrochemistry to test the chemical reactions taking placeon the electrode, which is not the way that actual batteries operate.Prior arts and literature publications have relied on this type ofcycling protocol to show high cycle life, however, on galvanostaticcycling there is rapid loss in capacity that leads to the immediatefailure of the battery. Also, the prior art has relied on makingelectrodes with excessive carbons (about 10 times more than MnO₂loading), to show high cycle life. However, batteries containingelectrodes with a 10 times excess of carbon are not economically viableand have very poor energy density that would be impractical in any realworld application. Extensive tests have shown that electrodes containing45 weight percent or more loadings of MnO₂ with bismuth incorporationlead to battery failure within 5 cycles.

BRIEF DESCRIPTION OF THE INVENTION

A secondary alkaline battery using manganese dioxide is described. Thebattery includes a mixed cathode material with birnessite-phasemanganese dioxide or electrolytic manganese dioxide (EMD), a bismuthcompound and a copper compound selected from the group consisting ofelemental copper and a copper salt. In some embodiments, a conductivecarbon and/or a binder may also be included. An advantage that may berealized in the practice of some disclosed embodiments of the battery isthat a MnO₂ alkaline battery is rendered rechargeable.

This brief description of the invention is intended only to provide abrief overview of subject matter disclosed herein according to one ormore illustrative embodiments, and does not serve as a guide tointerpreting the claims or to define or limit the scope of theinvention, which is defined only by the appended claims. This briefdescription is provided to introduce an illustrative selection ofconcepts in a simplified form that are further described below in thedetailed description. This brief description is not intended to identifykey features or essential features of the claimed subject matter, nor isit intended to be used as an aid in determining the scope of the claimedsubject matter. The claimed subject matter is not limited toimplementations that solve any or all disadvantages noted in thebackground.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the features of the invention can beunderstood, a detailed description of the invention may be had byreference to certain embodiments, some of which are illustrated in theaccompanying drawings. It is to be noted, however, that the drawingsillustrate only certain embodiments of this invention and are thereforenot to be considered limiting of its scope, for the scope of theinvention encompasses other equally effective embodiments. The drawingsare not necessarily to scale, emphasis generally being placed uponillustrating the features of certain embodiments of the invention. Inthe drawings, like numerals are used to indicate like parts throughoutthe various views. Thus, for further understanding of the invention,reference can be made to the following detailed description, read inconnection with the drawings in which:

FIG. 1 is a cross section view of an embodiment of the battery in aprismatic arrangement;

FIG. 2 is a cross section view of an embodiment of the positiveelectrode or cathode of the battery in a prismatic arrangement;

FIG. 3A is a graph illustrating charge and discharge curves of aMnO₂+Bi+Cu cathode, charged and discharged galvanostatically at a C/3rate using a NiOOH counter electrode; FIG. 3B is a graph illustratingthe charge and discharge curves of a similar battery as in (a) butwithout the Cu component of the mixed material.

FIG. 4A is a graph illustrating stable discharge capacity curves of aMnO₂+Bi+Cu cathodes for over 3700 cycles at manganese dioxide (MD)loadings of both 5% and 45%, charged and discharged galvanostatically ata 1 C rate using a NiOOH counter electrode; FIG. 4B is a graphillustrating the coulombic efficiency of the batteries in FIG. 4A; FIG.4C is a graph illustrating charge and discharge curves of the battery inFIG. 4A with 5% MD and KS44 as a conductive carbon; FIG. 4D is a graphillustrating charge and discharge curves of the battery in FIG. 4A with45% MD and carbon nanotubes (CNTs) as a conductive carbon.

FIG. 5 is a graph illustrating charge and discharge curves of a batterycomprising a pasted zinc anode, a microporous membrane separator, aMnO₂+Bi+Cu cathode, an alkaline electrolyte, and a battery housing. Thebattery was charged and discharged galvanostatically at a C/3 rate.

FIG. 6A shows cyclic voltammetry scan of the first ten cycles ofbirnessite-phase bismuth-MnO₂ mixed with CMC-PVA binder at 1 mV/secbetween 0.3 V and −1 V; FIG. 6B depicts cyclic voltammetry scan of thefirst ten cycles of Birnessite-phase bismuth-MnO₂ mixed with TEFLON®brand polytetrafluoroethylene binder at 1 mV/sec between 0.3 V and −1 V;FIG. 6C shows cyclic voltammetry scan of various cycles ofbirnessite-phase bismuth-MnO₂ mixed with CMC-PVA at 1 mV/sec between 0.3V and −1 V showing less overpotentials and impedance with increasingcycle numbers; FIG. 6D depicts cyclic voltammetry scan of various cyclesof birnessite-phase bismuth-MnO₂ mixed with TEFLON® at 1 mV/sec between0.3 V and −1 V showing increasing overpotentials and impedance withincreasing cycle numbers. The numbers on the diagram represent cyclenumbers, and the potential was increased to 0.4 V after 120 cycles.

FIG. 7A depicts a plot of Specific charge and discharge capacity andcoulombic efficiency versus cycle number for birnessite-phasebismuth-MnO₂ mixed with CMC-PVA at 1 mV/sec between 0.3 V and −1 V; FIG.7B shows a plot of specific charge and discharge capacity and coulombicefficiency versus cycle number for birnessite-phase bismuth-MnO₂ mixedwith TEFLON® at 1 mV/sec between 0.3 V and −1 V. (Charge potentialincreased to 0.4 V after 120 cycles);

FIG. 8A shows a cyclic voltammetry scan of the first ten cycles ofbirnessite-phase bismuth-MnO₂ mixed with CMC-PVA binder and Ni additiveat 1 mV/sec between 0.3 V and −1 V; FIG. 8B depicts a cyclic voltammetryscan of the first ten cycles of birnessite-phase bismuth-MnO₂ mixed withCMC-PVA binder at 1 mV/sec between 0.3 V and −1 V; FIG. 8C shows acyclic voltammetry scan of various cycles of birnessite-phasebismuth-MnO₂ mixed with CMC-PVA and Ni at 1 mV/sec between 0.3 V and −1V showing no overpotentials for the major 1^(st) and 2^(nd) electronreactions with increasing cycle numbers; FIG. 8D depicts a cyclicvoltammetry scan of various cycles of birnessite-phase bismuth-MnO₂mixed with only CMC-PVA at 1 mV/sec between 0.3 V and −1 V showingslight increase in overpotentials and impedance with increasing cyclenumbers;

FIG. 9A depicts galvanostatic cycling of 45 wt. % birnessite-type MnO₂mixed with 45 wt. % carbon nanotubes at 1 C while FIG. 9B showsgalvanostatic cycling of 45 wt. % birnessite-type MnO₂ mixed with 40 wt.% graphite and 5 wt. % carbon nanotubes at C/3;

FIG. 9C depicts galvanostatic cycling of different loadings EMD-typeMnO₂ mixed with carbon nanotubes at 1 C while FIG. 9D illustratesgalvanostatic cycling of 75 wt. % EMD-type MnO₂ mixed with 10 wt. %carbon nanotubes at different rates.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1 a battery 10 has a housing 6, a cathode currentcollector 1, a cathode material 2, a separator 3, an anode currentcollector 4, and an anode material 5. FIG. 1 shows a prismatic batteryarrangement. In another embodiment, the battery is a cylindricalbattery. An electrolyte is dispersed in an open space throughout battery10. Referring to FIG. 2 the cathode current collector 1 and cathodematerial 2 are collectively called either the cathode 12 or the positiveelectrode 12.

The art described in this disclosure is with regards to the developmentof rechargeable alkaline cells that employ a mixed material in thecathode 12. The mixed material is a combination of manganese dioxide(MnO₂, also referred to as MD), bismuth, and copper. In one embodiment,conductive carbon is also present in the cathode 12. The cathode 12 isincorporated into the battery 10 which may be a secondary battery. Themixed material is based on one or many polymorphs of MnO₂, includingelectrolytic (EMD), α-MnO₂, β-MnO₂, γ-MnO₂, δ-MnO₂, ε-MnO₂, or λ-MnO₂.In general the cycled form of manganese dioxide in the cathode is δ-MnO₂which is interchangeably referred to as birnessite. If non-birnessitepolymorphic forms of manganese dioxide are used, these are converted tobirnessite in-situ by one or more conditioning cycles. For example, afull discharge to the end of the MnO₂ second electron stage may beperformed and subsequently recharging back to its Mn⁴⁺ state, resultingin birnessite-phase manganese dioxide.

In one embodiment, the cathode material comprises 2-30% wt conductivecarbon, 0-30% conductive metal additive, 1-70% wt. copper compound,1-20% wt bismuth compound, 0-10% wt binder and birnessite or EMD. Inanother embodiment the cathode material comprises 2-30% wt conductivecarbon, 0-30% conductive metal additive, 1-20% wt bismuth compound,0-10% wt binder and birnessite or EMD. In one embodiment, the cathodematerial consists essentially of 2-30% wt conductive carbon, 0-30%conductive metal additive, 1-70% wt. copper compound, 1-20% wt bismuthcompound, 0-10% wt binder and the balance birnessite or EMD. In anotherembodiment the cathode material consists essentially of 2-30% wtconductive carbon, 0-30% conductive metal additive, 1-20% wt bismuthcompound, 0-10% wt binder and the balance birnessite or EMD.

Range Component (% wt) conductive carbon 2-30% conductive 0-30% metaladditive copper compound 1-70% bismuth compound 1-20% binder 0-10% MnO₂compound Balance

The mixed material includes a bismuth compound and copper, which aretogether allow galvanostatic battery cycling of the cathode. The bismuthcompound is incorporated into the cathode 12 as an inorganic or organicsalt of bismuth (oxidation states 5, 4, 3, 2, or 1), as a bismuth oxide,or as bismuth metal (i.e. elemental bismuth). The bismuth compound ispresent in the cathode material at a concentration between 1-20 wt %.Examples of inorganic bismuth compounds include bismuth chloride,bismuth bromide, bismuth fluoride, bismuth iodide, bismuth sulfate,bismuth nitrate, bismuth trichloride, bismuth citrate, bismuthtelluride, bismuth selenide, bismuth subsalicylate, bismuthneodecanoate, bismuth carbonate, bismuth subgallate, bismuth strontiumcalcium copper oxide, bismuth acetate, bismuthtrifluoromethanesulfonate, bismuth nitrate oxide, bismuth gallatehydrate, bismuth phosphate, bismuth cobalt zinc oxide, bismuth sulphiteagar, bismuth oxychloride, bismuth aluminate hydrate, bismuth tungstenoxide, bismuth lead strontium calcium copper oxide, bismuth antimonide,bismuth antimony telluride, bismuth oxide yittia stabilized,bismuth-lead alloy, ammonium bismuth citrate, 2-napthol bismuth salt,duchloritri(o-tolyl)bismuth, dichlordiphenyl(p-tolyl)bismuth,triphenylbismuth.

The copper compound is incorporated into the cathode 12 as an organic orinorganic salt of copper (oxidation states 1, 2, 3 or 4), as a copperoxide, or as copper metal (i.e. elemental copper). The copper compoundis present in a concentration between 1-70 wt %. In one embodiment, thecopper compound is present in a concentration between 5-50 wt %. Inanother embodiment, the copper compound is present in a concentrationbetween 10-50 wt %. In yet another embodiment, the copper compound ispresent in a concentration between 5-20 wt %. Examples of coppercompounds include copper and copper salts such as copper aluminum oxide,copper (I) oxide, copper (II) oxide and/or copper salts in a +1, +2, +3,or +4 oxidation state including, but not limited to, copper nitrate,copper sulfate, copper chloride, etc. The effect of copper is to alterthe oxidation and reduction voltages of bismuth. This results in acathode with full reversibility during galvanostatic cycling, ascompared to a bismuth-modified MnO₂ which will not withstandgalvanostatic cycling. This is shown in the discussion of FIG. 3A andFIG. 3B.

The addition of the conductive carbon enables high loadings of MnO₂ inthe mixed material, resulting in high volumetric and gravimetric energydensity. The conductive carbon is present in a concentration between2-30 wt %. Such conductive carbon include single walled carbonnanotubes, multiwalled carbon nanotubes, graphene, carbon blacks ofvarious surface areas, and others that have specifically very highsurface area and conductivity. Higher loadings of the MnO₂ in the mixedmaterial electrode are, in some embodiments, desirable to increase theenergy density. Other examples of conductive carbon include TIMREXPrimary Synthetic Graphite (all types), TIMREX Natural Flake Graphite(all types), TIMREX MB, MK, MX, KC, B, LB Grades (examples, KS15, KS44,KC44, MB15, MB25, MK15, MK25, MK44, MX15, MX25, BNB90, LB family) TIMREXDispersions; ENASCO 150G, 210G, 250G, 260G, 350G, 150P, 250P; SUPER P,SUPER P Li, carbon black (examples include Ketjenblack EC-300J,Ketjenblack EC-600JD, Ketjenblack EC-600JD powder), acetylene black,carbon nanotubes (single or multi-walled), graphene, graphyne, grapheneoxide, and combinations thereof.

The addition of conductive metal additives to the mixed material cathodemay be accomplished by addition of nickel powder to the MnO₂+Bi+Cumixture. The conductive metal additive is present in a concentration of0-30 wt %. The conductive metal additive may be, for example, nickel,copper, silver, gold, tin, cobalt, antimony, brass, bronze, aluminum,calcium, iron or platinum. In one embodiment, the conductive metaladditive is a powder. In one embodiment, a second conductive metaladditive is added to act as a supportive conductive backbone for thefirst and second electron reactions to take place. The second electronreaction has a dissolution-precipitation reaction where Mn³⁺ ions becomesoluble in the electrolyte and precipitate out on the graphite resultingin an electrochemical reaction and the formation of manganese hydroxide[Mn(OH)₂] which is non-conductive. This ultimately results in a capacityfade in subsequent cycles. Suitable second additives include transitionmetals like Ni, Co, Fe, Ti and metals like Ag, Au, Al, Ca. Salts or suchmetals are also suitable. Transition metals like Co also help inreducing the solubility of Mn³⁺ ions. Such conductive metal additivesmay be incorporated into the electrode by chemical means or by physicalmeans (e.g. ball milling, mortar/pestle, spex mixture). An example ofsuch an electrode comprises 5-95% birnessite, 5-95% conductive carbon,0-50% second conductive metal additive and 1-10% binder.

In some embodiments a binder is used. The binder is present in aconcentration of 0-10 wt %. In one embodiment, the binder compriseswater-soluble cellulose-based hydrogels, which were used as thickenersand strong binders, and have been cross-linked with good mechanicalstrength and with conductive polymers. The binder may also be acellulose film sold as cellophane. The binders were made by physicallycross-linking the water-soluble cellulose-based hydrogels with a polymerthrough repeated cooling and thawing cycles. In one embodiment, 0-10 wt.% carboxymethyl cellulose (CMC) solution was cross-linked with 0-10 wt.% polyvinyl alcohol (PVA) on an equal volume basis. The binder, comparedto the traditionally-used TEFLON®, shows superior performance. TEFLON®is a very resistive material, but its use in the industry has beenwidespread due to its good rollable properties. This, however, does notrule out using TEFLON® as a binder. Mixtures of TEFLON® with the aqueousbinder and some conductive carbon were used to create rollable binders.Using the aqueous-based binder helps in achieving a significant fractionof the two electron capacity with minimal capacity loss over 350 cycles.In one embodiment, the binder is water-based, has superior waterretention capabilities, adhesion properties, and helps to maintain theconductivity relative to identical cathode using a TEFLON® binderinstead. Examples of hydrogels include methyl cellulose (MC),carboxymethyl cellulose (CMC), hydroypropyl cellulose (HPH),hydroypropylmethyl cellulose (HPMC), hydroxethylmethyl cellulose (HEMC),carboxymethylhydroxyethyl cellulose and hydroxyethyl cellulose (HEC).Examples of crosslinking polymers include polyvinyl alcohol,polyvinylacetate, polyaniline, polyvinylpyrrolidone, polyvinylidenefluoride and polypyrrole. In one such embodiment, a 0-10 wt % solutionof water-cased cellulose hydrogen is cross linked with a 0-10% wtsolution of crosslinking polymers by, for example, repeated freeze/thawcycles, radiation treatment or chemical agents (e.g. epichlorohydrin).The aqueous binder may be mixed with 0-5% TEFLON® to improvemanufacturability. The birnessite discharge reaction comprises adissolution-precipitation reaction where Mn³⁺ ions become soluble andprecipitate out on the conductive carbon as Mn²⁺. This second electronprocess involves the formation of a non-conductive manganese hydroxide[Mn(OH)₂] layer on the conductive graphite.

The cathodes 12 can be produced using methods implementable inlarge-scale manufacturing. The cathode 12 is capable of delivering thefull second electron capacity of 617 mAh/g of the MnO₂. Referring toFIG. 3A the cycling performance of a mixed material MnO₂+Bi+Cu cathodeis shown with complete galvanostatic rechargeability to 617 mAh/g-MnO₂.The addition of copper or salts of copper was done through eitherchemical/electrochemical synthesis or through physical means (e.g.mechanically pressing the bernessite/bismuth, conductive carbon pasteabout a copper support. Previous literature has focused on a MnO₂+Bimixed material, which does not show good galvanostatic rechargeabilityand fails by the fifth cycle, as shown in FIG. 3B.

Excellent rechargeable performance can be achieved for both low and highloadings of MnO₂ in the mixed material, allowing the cell/battery toachieve very high practical energy densities. FIG. 4A, FIG. 4B, FIG. 4Cand FIG. 4D show discharge capacity for two mixed material cathodes,achieving greater than 3700 cycles in both cases. One cathode containedMnO₂ at a total mass loading of 5% of the cathode material 2, using theconductive carbon KS44 graphite. The other cathode contained MnO₂ at atotal mass loading of 45% of the cathode material, with carbon nanotubes(CNTs) as the conductive carbon. The coulombic efficiency of both wasnearly 100%. The charge and discharge curves of these cathodes are seenin FIG. 4C and FIG. 4D respectively. The performance of the mixedmaterial can be maintained or enhanced, if needed, by the use of novelaqueous-based binders, additional conductive metal additives, and veryconductive carbons.

The resulting cathode may have a porosity in the range of 20%-85% asdetermined by mercury infiltration porosimetry. In one embodiment, theporosity is measured according to ASTM D4284-12 “Standard Test Methodfor Determining Pore Volume Distribution of Catalysts and CatalystCarriers by Mercury Intrusion Porosimetry.

In some embodiments birnessite-phase MnO₂ was synthesized in situ bybeginning with electrolytic manganese dioxide (EMD) in the mixedmaterial and performing a formation step by fully discharging to the endof the MnO₂ second electron stage (617 mAh/g-MnO₂ or the Mn²⁺ state) andrecharging back to the Mn⁴⁺ state, resulting in birnessite-phasemanganese dioxide (δ-MnO₂).

In some embodiments, a method was developed for the synthesis ofbirnessite-phase manganese dioxide. A 4-10 mole ratio betweenpermanganates to manganese sulfates was used. Solutions of therespective precursors were made and filled in a TEFLON®-lined containerthat fits inside a hydrothermal reactor. Bismuth could be used at thispoint or in the post-processing steps where an ion-exchange reactionoccurs. Irrespective of the point of bismuth incorporation, a suitableamount of bismuth nitrate, depending on the molar ratio of manganese tobismuth desired in the final product, was added to the solution witharound 10 mL of nitric acid. In one embodiment, the hydrothermal reactoris maintained between 130-170° C. for 10-16 hours to obtain the desiredbirnessite-phase of manganese dioxide doped with bismuth. Similarly, inthe ion-exchange procedure, the solutions are preferably stirred forlonger periods of time to facilitate better exchange. X-ray diffractionspectrums verify the formation the pure birnessite-phase, and scanningelectron images show circular lamellar-like nanostructures.

In some embodiments a second method was used for the synthesis ofbirnessite-phase MnO₂, similar to the method disclosed in Wadsley (JACS,Vol 72, 1781, 1950) or Yao's method mentioned in U.S. Pat. No.4,520,005. However, this method utilizes inexpensive and saferprecursors like manganese chloride instead of nitrates. The source ofbismuth could be any bismuth-containing salt including, for example,bismuth chloride. A solution of manganese and bismuth chloride wascreated depending on the ratio of manganese to bismuth desired in thefinal product. Around 10 ml of nitric acid was added to themanganese-bismuth solution. A strong solution of alkaline hydroxide(e.g. sodium hydroxide) was created and chilled to 0° C. The chilledsodium hydroxide solution was added to manganese-bismuth solution. Thesolution was oxidized by either bubbling oxygen or through addinghydrogen peroxide solution (e.g. 0.1-50% w/w). The crystallinity of thefinal phase of the product depended on the oxidation time. After thereaction was complete, the final product was thoroughly washed withdeionized water and weak acid.

The cathode 12 was tested while incorporated in the battery 10 thatcomprised the housing 6, the cathode 12 supported in the housing 6,various negative electrodes (including the anode current collector 4 andanode material 5) supported in the housing 6, the separator 3 depositedbetween the cathode 12 and negative electrode, and an alkalineelectrolyte (e.g. an alkaline hydroxide, such as NaOH, KOH, LiOH, ormixtures thereof) contained within the housing 6. The electrolyte mayhave a concentration of between 5% and 50% w/w. The cathode currentcollector 1 and the anode current collector 4 may be a conductivematerial, for example, nickel, nickel-coated steel, tin-coated steel,silver coated copper, copper plated nickel, nickel plated copper orsimilar material. The cathode current collector 1 and/or the anodecurrent collector 4 may be formed into an expanded mesh, perforatedmesh, foil or a wrapped assembly. In one embodiment, the cathode currentcollector is copper-free to prevent or minimize corrosion.

In one embodiment, the cathode material 2 is adhered to the cathodecurrent collector 1 by pressing at, for example, a pressure between1,000 psi and 20,000 psi (between 6.9×10⁶ and 1.4×10⁸ Pascals). Thecathode material 2 may be adhered to the cathode current collector 1 asa paste. A tab of each current collector extends outside of the deviceand covers less than 0.2% of the electrode area. The separator 3 clearlydemarcates the cathode 12 from the negative electrode. The separator 3may be a polymeric separator (e.g. cellophone, sintered polymer film, ora hydrophilically modified polyolefin). As used in this specification,the phrase “hydrophilically modified polyolefin” refers to a polyolefinwhose contact angle with water is less than 45°. In another embodiment,the contact angle with water is less than 30°. In yet anotherembodiment, the contact angle with water is less than 20°. Thepolyolefin may be modified by, for example, the addition of TRITONX-100™ or oxygen plasma treatment. The battery 10 was demonstrated toprovide high depth of discharge of about 617 mAh/g-MnO₂ for many morecycles than achievable with a simpler MnO₂+Bi cathode materialcontaining no Cu.

Electrochemical cells were tested with a variety of negative electrodes,including zinc, nickel oxyhydroxide (NiOOH), iron, cadmium and metalhydride (MH). Electrochemical cells with NiOOH negative electrodes weregenerally used for proof of concept, as it was known that NiOOH has noeffect on the mixed material cathode. This was the case in FIG. 3A, FIG.3B, FIG. 4A, FIG. 4B, FIG. 4C and FIG. 4D. A battery with a zincnegative electrode produces a significant and useful cell voltageenabling its use as a secondary battery. Electrochemical cells of thistype were cycled, as in FIG. 5. In these cases additional measures wereused to avoid any deleterious effect zincate ions may have on the mixedmaterial cathode, as zinc electrodes release zincate into the alkalineelectrolyte. One method used was a wrapped electrode design of thecathode. A second method used was utilizing CELGARD® brand microporousseparator, for the separator 3. Both of these methods gave good resultsand resulted in thousands of cycles. Thus these demonstrated a (mixedmaterial cathode) MnO₂—Zn battery. Charge and discharge curves of such abattery are shown in FIG. 5.

In some embodiments, the disclosed battery delivers high energy density(e.g. greater than 50 Wh/L), at a high depth of discharge (e.g. greaterthan 50% of the second electron capacity, i.e. greater than 318mAh/g-MnO₂) and high C-rates (e.g. greater than 1 C). In one embodiment,the depth of discharge is greater than 90% of the second electroncapacity after ten cycles.

In one embodiment, the birnessite is formed using a hydrothermalreaction that comprises mixing a strong oxidizing agent with a manganesesalt (e.g. manganese sulfate) in a hydrothermal reactor. Examples ofsuitable strong oxidizing agents include oxygen, hydrogen peroxide (e.g.50% w/w), peracetic acid, aromatic peroxides, potassium permanganate,sodium permanganate, ammonium permanganate, calcium permanganate,potassium persulfate, sodium, persulfate and ammonium persulfate. In onesuch embodiment, the mole ratio of the strong oxidizing agent to themanganese salt is about 1:1. The hydrothermal reaction may also includemixing bismuth nitrate with nitric acid to the oxidized manganese salt.For example, 1-30 mmol of manganese sulfate may be mixed with 1-30 mmolof the strong oxidizing agent along with 0-30 mmol of bismuth nitrateand 0-20 mL of nitric acid. The hydrothermal reaction may be kept at atemperature of between 80° C. and 250° C. for 1-72 hours. The bismuthand/or copper may optionally be incorporated into a layered birnessitecomposition through a post-processing ion-exchange reaction. Forexample, 0-30 mmole of bismuth nitrate and/or copper nitrate may bemixed with 0-20 mL of nitric acid to form a layered birnessite.

In another embodiment, the MnO₂ is formed by mixing manganese chloride(e.g. 0-5M) with bismuth chloride and/or copper chloride (e.g. 0-30mmol) and 0-20 mL of nitric acid in chilled 1-10M solutions of alkalinehydroxides (NaOH, KOH, CsOH, LiOH, etc.). In one embodiment, the chilledsolutions are between 0-10° C. The solution may be oxidized for between0.5-24 hours. After formation, the resulting cathode is washedthoroughly with deioinized water and a dilute acid (e.g. sulfuric acid).

Example 1

To test the effect of adding copper metal or its derivatives to themixed material cathode, two electrodes were made, a controlled electrodewhere there was no copper in the mix and an electrode where there wascopper. Both the electrodes contained electrolytic manganese dioxide(EMD) and a bismuth oxide as an additive. The cathode with copper wasmade by mixing 1.3 g MnO₂ (Tronox), 0.26 g Bi₂O₃, 1.04 g carbonnanotubes (CNTs), and 0.29 g CMC-PVA as a binder. To the resulting pastewas added 2.82 g of copper metal. Thus the final composition of thecathode material was (by mass) 22.8% MnO₂, 4.6% Bi₂O₃, 18.2% CNTs, 5.1%binder, and 49.3% copper. The resulting cathode material was pressed ona 6 in² nickel mesh which was the cathode current collector. Theelectrode was dried. The electrode with the copper additive will bementioned as mixed material cathode. The control cathode without copperwas made identically, with the same masses of materials, excludingcopper.

The mixed material cathode and the control cathode were compressed withNiOOH anodes in a prismatic box. A cellulosic separator was used toseparate the cathode and anode. A mercury/mercury oxide referenceelectrode was used to monitor the potentials of the cathode. The cellwas filled with 9M potassium hydroxide. The cathode was cycled between0.3 V and −1 V versus the reference at C/3.

A comparison of the charge and discharge curves for the first 5 cyclesof the cathodes are shown in FIG. 3A. The control cathode performance isshown in FIG. 3B. It initially discharges a capacity of around 500mAh/g, but it quickly deteriorates to around 50 mAh/g in the fifthcycle. The bismuth additive by itself is not an effective additive tomake the electrode galvanostatically rechargeable and this causescatastrophic electrode failure within a span of 5 cycles. Theadvantageous effect of the copper additive to the mixed material cathodeis shown in FIG. 3A. Cyclic voltammogram experiments on versions of themixed material cathode have demonstrated that the copper iselectrochemically active to the extent of about 2 mg of copper persquare inch of the electrode. Thus, while present in a large amount, thecopper acts as an additive and the vast majority of the cycled cathodecapacity (>90%) is due to MnO₂. The mixed material cathode is fullyrechargeable to the 2^(nd) electron capacity without any deterioration.The stability of the cycling curves also indicates it to be a verysteady and reliable cathode. The first discharge cycle demonstrates atypical EMD discharge curve, after which the birnessite-phase MnO₂ isformed after the first charge. Second discharge cycle onwards a typicalbirnessite discharge curve is seen. For the first time in literature,rechargeable galvanostatic cycling of a high-loading MnO₂ containingcathode to its full 2^(nd) electron capacity is shown.

Example 2

This example was meant to demonstrate that the mixed material cathodescould be fabricated using various conductive carbons. Agraphite-containing mixed material cathode was fabricated by mixing 19.2mg bismuth-modified MnO₂, 161.3 mg KS44 graphite, and 88.2 mg CMC-PVA asa binder. To the resulting paste was added 470 mg of copper metal. Thusthe final composition of the cathode material was (by mass) 2.6%Bi-MnO₂, 21.8% graphite, 11.9% binder, and 63.6% copper. The molar ratioof Mn chloride to Bi chloride used in the reaction to make thebirnessite-phase bismuth-MnO₂ was 8:1. CMC-PVA comprised 10 wt. % of theelectrode mix. This cathode material was pressed on a 1 sq in. nickelmesh and the electrode was dried. For comparison a CNT-containing mixedmaterial cathode was fabricated by mixing 135.9 mg MnO₂, 27.2 mg Bi₂O₃,108.7 mg CNTs, and 30.2 mg CMC-PVA as a binder. To the resulting pastewas added 470 mg of copper metal. Thus the final composition of thecathode material was (by mass) 17.6% MnO₂, 3.5% Bi₂O₃, 14.1% CNTs, 3.9%binder, and 60.9% copper. As in the case with graphite this cathodematerial was pressed on a 1 sq in. nickel mesh and the electrode wasdried.

These mixed material cathodes demonstrated that while good results canbe observed with either graphite or CNTs, a higher MnO₂ mass loading canbe achieved with CNTs as the conductive carbon. Thus thegraphite-containing cathode will be termed “low-loading” and theCNT-containing cathode will be termed “high-loading.” The mixed materialcathodes were compressed with NiOOH anodes in a prismatic box. Amercury/mercury oxide reference electrode was used to monitor thepotentials of the cathode. The cell was filled with 9M potassiumhydroxide. The cathode was cycled between 0.3V and −1V versus thereference at 1 C.

The performance of the mixed material cathodes is shown in FIG. 4A, FIG.4B, FIG. 4C and FIG. 4D. The long cycle life of these cathodes is shownin FIG. 4A, where there is no loss in capacity even after 4000 cyclesfor the low-loading and after approximately 3700 cycles for thehigh-loading cathodes, respectively. The coulombic efficiency is around100% for these cells as well. FIG. 4C and FIG. 4D show the charge anddischarge curves for the low-loading and high-loading electrodes,respectively. The important feature that the curves illustrate are themaintenance of the capacity curves at the same potentials and the full2^(nd) electron capacity. This has never been reported in literature fora MnO₂ containing cathode irrespective of mass loading percentages.

Example 3

The performance of the mixed material cathode was tested against a zincelectrode in a battery. The mixed material cathode was made by mixing0.55 g MnO₂ (Tronox), 0.11 g Bi₂O₃, and 0.44 g carbon nanotubes (CNTs),with no binder. Instead of binder a few drops of water was used to formthe initial paste. To this paste was added 0.47 g of copper metal. Thusthe final composition of the cathode material was (by mass) 35% MnO₂, 7%Bi₂O₃, 28% CNTs, and 30% copper. The resulting cathode material waspressed on a 6 in² nickel mesh which was then wrapped around the cathodematerial. The zinc electrode comprised of 13.6 g zinc powder, 1.6 g zincoxide, and 0.8 g TEFLON®. The zinc anode was pasted and pressed on acopper mesh. Both electrodes were dried.

The mixed material cathode was compressed with zinc anodes in aprismatic box. The cell was filled with 6M potassium hydroxide. Thecathode was cycled between 0.4 and 1.75V versus the zinc at C/3.

FIG. 5 shows the charge and discharge capacity curves for the (mixedmaterial cathode) MnO₂—Zn battery. The rechargeable characteristicfeatures of this battery are clearly seen at the 101th cycle. This showsa mixed material cathode MnO₂—Zn battery can be rechargeable withoutsignificant fade to thousands of cycles.

Example 4

To reduce the mass loading of copper, and increase the mass loading ofMnO2, an high-loading mixed material cathode was produced. The cathodewith was made by mixing 7.84 g MnO₂ (Tronox), 0.9 g Bi₂O₃, and 2.82 gcarbon nanotubes (CNTs). To the resulting paste was added 2.82 g ofcopper metal. Thus the final composition of the cathode material was (bymass) 55.9% MnO₂, 6.4% Bi₂O₃, 17.6% CNTs, and 20.1% copper. Theresulting cathode material was pressed on a 6 in² nickel mesh which wasthe cathode current collector. The electrode was dried.

This mixed material cathode was compressed with NiOOH anodes in aprismatic box. A cellulosic separator was used to separate the cathodeand anode. A mercury/mercury oxide reference electrode was used tomonitor the potentials of the cathode. The cell was filled with 9 Mpotassium hydroxide. The cathode was cycled between 0.3 V and −1 Vversus the reference at C/3.

Example 5

To test the effect of the binders, two different mixes, one containingCMC-PVA as the binder and the other TEFLON®, were made. As this examplewas meant to demonstrate the effectiveness of the CMC-PVA binder, nocopper was used in this electrode. The electrodes were made by mixing64.5 mg birnessite-phase bismuth-MnO₂, 1.097 g KS-44 graphite, and 130mg of the respective binder. The mix was pasted on nickel mesh andpressed. The electrode was dried.

The birnessite-phase bismuth-MnO₂ electrodes were compressed with NiOOHanodes in a prismatic box. A mercury/mercury oxide reference electrodewas used to monitor the potentials of the birnessite electrode. The cellwas filled with 9 M potassium hydroxide. The birnessite electrode wascycled between 0.3 V and −1 V versus the reference at 1 mV/sec.

FIG. 6A and FIG. 6B show potentiodynamic scans for the first ten cyclesfor the electrode made with CMC-PVA and TEFLON®, respectively. Therespective scans show an increase in peak height and width with increasein cycle number. The main difference in the performance of the binderscan be seen in the current density of the peaks. The electrodecontaining CMC-PVA clearly shows much higher current densities comparedto the electrode containing TEFLON®. Four peaks can be seen in thebottom half of the scan (negative current densities). The first peaknear −0.2 V represents the small conversion of Mn⁴⁺ ions to Mn³⁺ ions.The two peaks between −0.4 V and −0.7 V for both scans represent thefirst and second electron reactions where bulk of the Mn⁴⁺ getsconverted to Mn²⁺. The last peak represents the reduction of bismuthoxide. The position of the peaks with increasing cycle number seemstable for the CMC-PVA electrode, while the electrode containing TEFLON®seems to shift to more negative potentials. The end of the secondelectron reaction for the electrode containing TEFLON® is at a muchlower negative potential than that of CMC-PVA. The stability of theposition of the peaks is important during discharge as it indicates theconstant deliverance of energy at the same potential with increasingcycles. In the top-half section of the scan, three peaks are observedinitially for both the electrodes. The first two peaks are near −0.6 Vand −0.5 V, which indicate the oxidation of bismuth. The major peak isnear −0.1 V, which indicates the oxidation from Mn²⁺ to Mn⁴⁺. However,in FIG. 6B, for the electrode containing TEFLON®, an onset of a fourthpeak appears on the fourth cycle. This probably indicates that the Mn²⁺to Mn⁴⁺ is a two-step oxidation process. FIG. 6C and FIG. 6D show thelong-term cycling effects on the electrodes containing CMC-PVA andTEFLON®, respectively. The plots clearly show the advantages of usingCMC-PVA over TEFLON®. After 350 cycles, the major 1^(st) and 2^(nd)electron reaction peaks are visible for the electrode containingCMC-PVA, and more importantly, in the same range between −0.4 V and −0.6V, respectively. There is a slight shift in peak position due to a smallincrease in overpotential. The detrimental effects of TEFLON® can beseen in the first 50 cycles, where the peaks shift drastically to lowerpotentials in the discharge process. After 320 cycles, the reactionstaking place on the electrode containing TEFLON® have almost completelydiminished, delivering very little capacity. It is important to notethat the negative effects of TEFLON® are so overwhelming that it issufficient to negate the conductivity of an electrode containing 10times graphite.

FIG. 7A and FIG. 7B show the specific capacity fade for the electrodescontaining CMC-PVA and TEFLON®, respectively. For both the electrodes anincrease in capacity is observed for the first 50 cycles. However, forthe electrode containing TEFLON®, the capacity that can be drawn fromthe electrode is much lower than that compared to the one containingCMC-PVA. After 350 cycles, the electrode containing CMC-PVA has acapacity of around 300 mAh/g, while the electrode containing TEFLON® hasreduced drastically to around 50 mAh/g. FIG. 7B shows a good comparisonof the capacity fade between the two electrodes, and one of theadvantages of using CMC-PVA as a binder over TEFLON®.

Example 6

The purpose of this example was to show the effectiveness of addedconductive metal in the electrode, which served as a replacement forsome part of the conductive carbon. The electrodes were made by mixing52 mg birnessite-phase bismuth-MnO₂, 312 mg KS-44 graphite, and 208 mgnickel powder till the mixture was homogeneous. The balance of the mixwas 470 mg CMC-PVA used as a binder. The mix was pasted on nickel meshand pressed. The electrode was dried.

The birnessite-phase bismuth-MnO₂ electrodes were compressed with NiOOHanodes in a prismatic box. A mercury/mercury oxide reference electrodewas used to monitor the potentials of the birnessite electrode. The cellwas filled with 9 M potassium hydroxide. The birnessite electrode wascycled between 0.3 V and −1 V versus the reference at 1 mV/sec.

FIG. 8A and FIG. 8B show the potentiodynamic scans for the first tencycles for the electrode containing CMC-PVA with Ni and only CMC-PVA,respectively. The respective scans show an increase in peak height andwidth with increase in cycle number. Four peaks can be seen in thebottom half of the scan (negative current densities). The first peaknear −0.2 V represents the small conversion of Mn⁴⁺ ions to Mn³⁺ ions.The two peaks between −0.4 V and −0.7 V for both scans represent thefirst and second electron reactions where bulk of the Mn⁴⁺ getsconverted to Mn²⁺. The last peak represents the reduction of bismuthoxide. The position of the peaks with increasing cycle number seemstable for the CMC-PVA with Ni electrode, while the electron containingonly CMC-PVA seems to shift slightly to more negative potentials. In thetop-half section of the scan, three peaks are observed for the electrodecontaining only CMC-PVA, while for the electrode containing CMC-PVA withNi, initially, four peaks are observed. The first two peaks are near−0.6 and −0.5 V, which indicate the oxidation of bismuth. For theelectrode containing only CMC-PVA, the major peak is near −0.1 V, whichindicates the oxidation from Mn²⁺ to Mn^(4±). However, in FIG. 8A, forthe electrode containing CMC-PVA with Ni, the manganese oxidation stepappears to be a two-step process, but the formation of a shoulder peakon the main peak near −0.1 V indicates a much more complicated oxidationprocess which is depended on conductivity. FIG. 8C and FIG. 8D show thelong-term cycling effects on the electrodes containing CMC-PVA with Niand only CMC-PVA, respectively. The plots clearly show the advantage ofusing a second conductive metal additive. After 350 cycles, the major1^(st) and 2^(nd) electron reaction peaks remain at the same potentialsfor the electrode containing CMC-PVA with Ni, while the electrodecontaining only CMC-PVA experiences a shift due to an increase inoverpotential. It is also important to note the reduction in the currentdensity peak height for the electrode containing only CMC-PVA (FIG. 8D).The reduction in peak height corresponds to a loss in capacity, which isquite rapid for the electrode containing only CMC-PVA.

Example 7

A first electrode was constructed by mixing 0.7 g of birnessite-typeMnO₂ with 0.7 g carbon nanotubes until the mixture was homogeneous. Thebalance of the mix was 0.16 g CMC-PVA. The electrode mix was pasted on acopper mesh, pressed and dried. This electrode was cycledgalvanostatically at a 1 C rate.

A second electrode was constructed by mixing 0.7 g EMD-type MnO₂(Tronox) with 0.56 g carbon nanotubes and 0.14 g Bi₂O₃ until the mixturewas homogeneous. The balance of the mix was 0.16 g CMC-PVA. Theelectrode mix was pasted on a copper mesh, pressed and dried. Thiselectrode was cycled galvanostatically at a 1 C rate.

A third electrode was constructed by mixing 0.7 g of birnessite-typeMnO₂ with 0.62 g graphite (KS44) and 0.08 g carbon nanotubes. Thebalance was 0.16 g CMC-PVA. The mix was pasted on a copper mesh andpressed. The electrode was dried. This electrode was cycledgalvanostatically at a C/3 rate.

A fourth electrode was constructed by mixing 0.94 g of EMD-type MnO₂with 0.19 g Bi₂O₃ and 0.07 g carbon nanotubes. The balance was 0.36 gCMC-PVA binder. The electrode mixes were pasted on a copper mesh,pressed and dried. The electrode was cycled galvanostatically at a 1 Crate.

A fifth electrode was constructed by mixing 1.16 g of EMD-type MnO₂,0.16 g Bi₂O₃, and 0.16 g carbon nanotubes. The balance was 0.08 g ofCMC-PVA binder. The electrode mix was pasted on a copper mesh, pressedand dried. This 75 wt. % electrode was cycled at both C/3 and C/5 rates.

The electrodes were compressed with the nickel anodes in a prismaticbox. A mercury/mercury oxide reference electrode was used to monitor thepotentials. A cell was filled with 9M potassium hydroxide. Thebirnessite electrode was cycled galvanostatically between 0.3V and −1Vversus the reference.

FIG. 9A, FIG. 9B, FIG. 9C and FIG. 9D show galvanostatic cycling datafor the different electrodes and their respective loadings and rates.FIG. 9A shows the cycling of 45 wt. % loading of birnessite-type MnO₂and 45 wt % carbon nanotubes (the first electrode), where initially ahigh capacity was obtained that steadily increased to about 20 cycles,after which, the complete second electron capacity was obtained. FIG. 9Bshows the cycling results of a 45 wt. % loading birnessite-type MnO₂mixed with 40 wt. % graphite and 5 wt. % carbon nanotubes at C/3 (thethird electrode). A high capacity was also obtained, as seen in FIG. 9B,and after 70 cycles, the capacity was still around 450 mAh/g. FIG. 9Aand FIG. 9B demonstrate the important role of carbon nanotubes inincreasing the conductivity of the electrode and achieving maximumcapacity during cycling.

FIG. 9C shows the cycling results of higher loading EMD-type MnO₂ mixedwith carbon nanotube electrodes at 1 C. The 45 wt. % EMD-type MnO₂ with36 wt. % carbon nanotubes (the second electrode) achieves the completecapacity in the first cycle and remains consistent in subsequent cycles.The EMD-type MnO₂ transforms into birnessite-type MnO₂ during cycling.This behavior is very similar to the birnessite-type MnO₂ shown in FIG.9A. The 60 wt. % EMD-type MnO₂ mixed with 18 wt. % carbon nanotubes (thefourth electrode) also exhibits a very high capacity of around 420 mAh/gafter 120 cycles at very high rates of 1 C for charge and discharge.FIG. 9D shows the cycling results of 75 wt. % loading of EMD-type MnO₂with 10 wt. % carbon nanotubes (the fifth electrode) at C/3 and C/5rates. The cell running at C/3 has a capacity of around 350 mAh/g afteraround 30 cycles, and the cell running at C/5 has a capacity of around400 mAh/g after sixteen cycles. The results shown in FIGS. 9A-9Dindicate the importance of high conductive carbon sources in achievinghigh capacity for higher loadings of MnO₂ during cycling at rates ofinterest in the battery community.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

1. A method of producing a cathode, the method comprising steps of:mixing multiple ingredients to form a cathode paste, the multipleingredients comprising: a manganese oxide compound selected from thegroup consisting of: birnessite-phase manganese dioxide (δ-MnO2),electrolytic manganese dioxide (EMD), and combinations thereof; abismuth compound selected from the group consisting of: elementalbismuth, a bismuth salt, and combinations thereof; and a copper compoundcomprising elemental copper; pressing the cathode paste onto a cathodecurrent collector at a pressure between 6.9×106 and 1.4×108 Pascals toform a pressed assembly; drying the pressed assembly to produce acathode.
 2. The method as recited in claim 1, wherein the multipleingredients further comprises a conductive carbon.
 3. The method asrecited in claim 1, wherein the multiple ingredients further comprises abinder.
 4. The method as recited in claim 1, further comprising:simultaneously pressing the cathode paste onto the cathode currentcollector and onto a substrate of elemental copper to form the pressedassembly.
 5. The method of claim 1, wherein the manganese oxide compoundcomprises a non-birnessite-phase of manganese dioxide, and wherein themethod further comprises: performing one or more conditioning cycles onthe cathode, wherein each conditioning cycle of the one or moreconditioning cycles comprises: discharging the cathode to an end of themanganese dioxide compound second electron stage; recharging at least aportion of the manganese oxide compound back to a Mn4+ state; andconverting at least a portion of the non-birnessite phase of manganesedioxide into birnessite phase manganese dioxide as a result of thedischarging and recharging.
 6. The method of claim 1, wherein theelemental copper is in a powder form or a metallic support form, whereinthe metallic support form comprises at least one of a mesh, a foil, aningot, a sheet, or a wire.
 7. The method of claim 1, wherein the cathodematerial further comprises a conductive carbon, and wherein the cathodematerial consists essentially of greater than 0 wt. % and less than orequal to 30 wt. % of the conductive carbon; between 1-20 wt. % of thebismuth compound; between 1-70 wt. % of the copper compound; greaterthan 0 wt. % and less than or equal to 10 wt. % of a binder; and thebalance being the manganese oxide compound.
 8. The method of claim 1,wherein the elemental copper is a solid copper support.
 9. The method ofclaim 1, wherein the cathode material further comprises acellulose-based hydrogel binder.
 10. The method of claim 1, wherein thebismuth compound is bismuth oxide.
 11. A method of producing a battery,the method comprising steps of: producing a cathode, the cathodecomprising a cathode material comprising: a manganese oxide compoundselected from the group consisting of birnessite-phase manganese dioxide(δ-Mη02) and electrolytic manganese dioxide (EMD); a bismuth compoundselected from the group consisting of elemental bismuth and a bismuthsalt; and elemental copper, disposing the cathode into a housing;disposing an anode into the housing; disposing a polymeric separatorbetween the anode and the cathode such that the anode and the cathodeare separated; and adding an electrolyte to the housing.
 12. The methodof claim 11, wherein the cathode material further comprises a conductivecarbon.
 13. The method of claim 11, wherein the manganese oxide compoundis birnessite-phase manganese dioxide, the method further comprising astep of forming the birnessite-phase manganese dioxide using ahydrothermal reaction that comprises: oxidizing a manganese salt with anoxidizing agent to form an oxidized manganese salt; adding a bismuthsalt and an acid nitric acid to the oxidized manganese salt; maintaininga temperature of between 80° C. and 250° C. for 1-72 hours.
 14. Themethod of claim 13, further comprising a step of adding a copper salt tothe oxidized manganese salt.
 15. The method of claim 11, wherein themanganese oxide compound is birnessite-phase manganese dioxide, themethod further comprising a step of: forming the birnessite-phasemanganese dioxide by mixing manganese chloride with bismuth chloride andnitric acid in a chilled 1-10 M solution of alkaline hydroxide, whereinthe chilled 1-10M solution is between 0-10 C for 0.5-24 hours.
 16. Themethod of claim 15, wherein the step of mixing manganese chloridefurther comprises mixing copper chloride.
 17. The method of claim 15,wherein the step of mixing manganese chloride with the bismuth chloride,the copper chloride and the nitric acid occurs simultaneously.
 18. Themethod of claim 11, wherein the cathode material further comprises aconductive metal additive selected from the group consisting of: nickel,a nickel salt, a copper salt, silver, a silver salt, aluminum, analuminum salt, gold, a gold salt, iron, an iron salt, tin, a tin salt,cobalt, a cobalt salt, platinum, a platinum salt, brass, bronze, andcombinations thereof.
 19. The method of claim 11, wherein the elementalcopper is in a powder form or a metallic support form, wherein themetallic support form comprises at least one of a mesh, a foil, aningot, a sheet, or a wire.
 20. The method of claim 11, wherein theelemental copper is a solid copper support.
 21. The method of claim 11,wherein producing the cathode comprising the cathode material comprises:mixing an oxidizing agent with at least one manganese salt to form areaction mixture; placing the reaction mixture in a hydrothermalreactor; and maintaining the reaction mixture at a temperature for atime sufficient to form the manganese oxide compound, wherein themanganese oxide compound comprises a birnessite phase manganese dioxide.22. The method of claim 21, wherein the oxidizing agent comprises atleast one of oxygen, hydrogen peroxide, peracetic acid, aromaticperoxides, potassium permanganate, sodium permanganate, ammoniumpermanganate, calcium permanganate, potassium persulfate, sodium,persulfate, or ammonium persulfate.
 23. The method of claim 21, furthercomprising: combining a bismuth salt and an acid with the reactionmixture prior to maintaining the reaction mixture at the temperature forthe time, wherein the birnessite phase manganese dioxide comprisesbismuth within a layered birnessite composition.
 24. The method of claim21, further comprising: ion-exchanging the birnessite phase manganesedioxide with bismuth and copper.
 25. The method of claim 24, whereinion-exchanging the birnessite phase manganese dioxide with bismuth andcopper comprises: mixing a bismuth salt, a copper salt, and an acid withthe birnessite phase manganese dioxide; and forming a layered birnessitecomposition comprising bismuth and copper.
 26. The method of claim 21,wherein the manganese salt comprises a mixture of one or morepermanganates and one or more manganese sulfates, and wherein the methodfurther comprises: mixing bismuth nitrate and nitric acid with thereaction mixture; and forming a lamellar-like nanostructure of thebirnessite phase manganese dioxide doped with bismuth.
 27. The method ofclaim 11, wherein producing the cathode comprising the cathode materialcomprises: mixing manganese chloride, a bismuth salt, and an acid in areactor to form a reaction mixture; adding an alkaline hydroxide to thereaction mixture; oxidizing the reaction mixture; and forming, based onthe oxidizing, the manganese oxide compound comprising a birnessitephase manganese dioxide.
 28. The method of claim 27, wherein the bismuthsalt comprises bismuth chloride.
 29. The method of claim 27, furthercomprising: mixing a copper salt with the reaction mixture prior tooxidizing the reaction mixture.
 30. The method of claim 11, wherein thecathode material comprises a birnessite phase manganese dioxide, whereinthe bismuth compound comprises elemental bismuth, wherein the birnessitephase manganese dioxide has a lamellar-like nanostructure, and whereinthe birnessite phase manganese dioxide comprises the elemental bismuthand the elemental copper ion exchanged within the lamellar-likenanostructure.